Efficient Bioconversion of Chitinous Waste to N-Acetylchitobiose and N-Acetylglucosamine Using a Novel Salt-Tolerant Chitinase from Bacillus clausii

Efficientand sustainable approach for production of GlcNAcand (GlcNAc)(2) from chitinous waste using a salt-tolerantchitinase. Chitin, a highly insoluble and poorly degradable polymerderivedfrom seafood industry waste, can be converted into value-added productsincluding N-acetylchitobiose ((GlcNAc)(2)) and N-acetylglucosamine (GlcNAc) by chitinase,which can overcome the disadvantages of chemical degradation. Here,we identified a novel salt-tolerant chitinase (CHI) involved in chitindegradation from Bacillus clausii TCCC11004. Recombinant CHI (rCHI) displayed a great tolerance againsthigh concentrations of NaCl, maintaining 376% of its initial activityin a solution containing 0.6 M NaCl, which was about NaCl concentrationin seawater. Chitin binding domain (ChBD) engineering demonstratedthat rCHI's ChBD was beneficial for its NaCl resistance property.As a multifunctional chitinase, rCHI exhibited dual exochitinase activityand N-acetylglucosaminidase activity, but no hydrolyticactivity toward (GlcNAc)(2) when using colloidal chitin asa substrate, which made it different from the typical reported chitinases.As a result, (GlcNAc)(2) and GlcNAc achieved the maximumyield ((GlcNAc)(2): 25.73 mg/mL and GlcNAc: 3.25 mg/mL) byhydrolyzing colloidal chitin from crab shells using rCHI alone. Thisstudy reported a valuable chitinase with the above dual activitiesand provided an eco-friendly and sustainable approach for cost-effectivebioconversion of chitin-containing biowastes to bioactive (GlcNAc)(2) and GlcNAc.